A generalisation of Whitney's trick in dimension 4,
borromeanism and related questions

It is well known that the classical Whitney's trick for
2-submanifolds X and Y of a 1-connected
PL (or smooth)
4-manifold M does not work. It has not been noticed that the
obstruction to it lies in the topology of Borromean-like links in
S3. This gives a rise to an idea of simultaneous performing of the
Whitney-like trick with 2 or more Whitney pairs of intersection
points of X and Y. Under certain conditions such a trick (called a
Whitney's multitrick) turns out to be successful. The distinctive
feature of a multitrick is that it can be performed only collectively
which means that for each separate pair of Whitney's points the
classical trick does not work.